Need to conditionally display section only on successful a!queryEntity results

1. There is no exception handling mechanism in SAIL.
2. So developers rely on doing the checks in if(). And checking for null, empty output from SAIL expression evaluation.
3. The above is an error because when database connection is not available, SAIL expr. evaluation fails. Catching this exception is somethings that we would do in a traditional programming language.
4. If we had some function to check if the datastore connection is available - we could wrap this in a if() and avoid the exception on the UI. Technically the above error is an exception and Appian stops the SAIL evaluation immediately. The only way I see we can handle such scenario is by creating some external webservice/ping the database hostname:port to find if its running. Frankly - that is too much of effort.

1. There is no exception handling mechanism in SAIL.
2. So developers rely on doing the checks in if(). And checking for null, empty output from SAIL expression evaluation.
3. The above is an error because when database connection is not available, SAIL expr. evaluation fails. Catching this exception is somethings that we would do in a traditional programming language.
4. If we had some function to check if the datastore connection is available - we could wrap this in a if() and avoid the exception on the UI. Technically the above error is an exception and Appian stops the SAIL evaluation immediately. The only way I see we can handle such scenario is by creating some external webservice/ping the database hostname:port to find if its running. Frankly - that is too much of effort.

Good explanations and I agree with it all. I was hoping someone had accomplished #4 on your list.

Hi Wayne,

I actually did #4 a while back, but I'm sure it can be improved upon. I basically had a process always running that would ping a table in the specified database and if the ping was not successful after 10 seconds, a constant was set to False to indicate the connection was currently down, otherwise the constant would remain as True.

With this process constatly running, you would then be able to use the constant in and if() statement as @chetany indicated above.

If you're interested, I can package up the process I used and you can modify as you see fit,

Yes, I would like to give this a try. That db is so unstable I need to be able to prevent application trouble tickets when it isn't operational since it is just used for additional details in a grid.

Here is the application in 18.2 to import and review for those who may be interested.  The Query Database smart service will need to be updated to ping the database you're monitoring.

 

DB Connection Checker.zip